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Tue, 29 Sep 2020 08:22:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:53440 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729799AbgI2LfL (ORCPT ); Tue, 29 Sep 2020 07:35:11 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 31FDF23C90; Tue, 29 Sep 2020 11:28:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601378926; bh=e38EqGABZdZgZOTGBUSdaKwLOXI5KyOfBAC42dvHaUE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0DuW2YC38vgwzZT/+FF51TsepjW+kmFwZBzFK4vwcBUXGQHRKvxOIsIVlinDW4WOl 3yOD4cQBvEzGHnsFWsEdXhbu+692zHCdMxhKnWW+aCEbdKtZO726fnAcqhBKNCoGFI 6F7GWTIGiDiJDiZymL3t4BH46Erg6Q2bSTOFUV4w= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qian Cai , Andrew Morton , Marco Elver , Hugh Dickins , Linus Torvalds , Sasha Levin Subject: [PATCH 4.19 190/245] mm/swap_state: fix a data race in swapin_nr_pages Date: Tue, 29 Sep 2020 13:00:41 +0200 Message-Id: <20200929105956.224200570@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929105946.978650816@linuxfoundation.org> References: <20200929105946.978650816@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Qian Cai [ Upstream commit d6c1f098f2a7ba62627c9bc17cda28f534ef9e4a ] "prev_offset" is a static variable in swapin_nr_pages() that can be accessed concurrently with only mmap_sem held in read mode as noticed by KCSAN, BUG: KCSAN: data-race in swap_cluster_readahead / swap_cluster_readahead write to 0xffffffff92763830 of 8 bytes by task 14795 on cpu 17: swap_cluster_readahead+0x2a6/0x5e0 swapin_readahead+0x92/0x8dc do_swap_page+0x49b/0xf20 __handle_mm_fault+0xcfb/0xd70 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x715 page_fault+0x34/0x40 1 lock held by (dnf)/14795: #0: ffff897bd2e98858 (&mm->mmap_sem#2){++++}-{3:3}, at: do_page_fault+0x143/0x715 do_user_addr_fault at arch/x86/mm/fault.c:1405 (inlined by) do_page_fault at arch/x86/mm/fault.c:1535 irq event stamp: 83493 count_memcg_event_mm+0x1a6/0x270 count_memcg_event_mm+0x119/0x270 __do_softirq+0x365/0x589 irq_exit+0xa2/0xc0 read to 0xffffffff92763830 of 8 bytes by task 1 on cpu 22: swap_cluster_readahead+0xfd/0x5e0 swapin_readahead+0x92/0x8dc do_swap_page+0x49b/0xf20 __handle_mm_fault+0xcfb/0xd70 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x715 page_fault+0x34/0x40 1 lock held by systemd/1: #0: ffff897c38f14858 (&mm->mmap_sem#2){++++}-{3:3}, at: do_page_fault+0x143/0x715 irq event stamp: 43530289 count_memcg_event_mm+0x1a6/0x270 count_memcg_event_mm+0x119/0x270 __do_softirq+0x365/0x589 irq_exit+0xa2/0xc0 Signed-off-by: Qian Cai Signed-off-by: Andrew Morton Cc: Marco Elver Cc: Hugh Dickins Link: http://lkml.kernel.org/r/20200402213748.2237-1-cai@lca.pw Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/swap_state.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 09731f4174c7e..3febffe0fca4a 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -537,10 +537,11 @@ static unsigned long swapin_nr_pages(unsigned long offset) return 1; hits = atomic_xchg(&swapin_readahead_hits, 0); - pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages, + pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits, + max_pages, atomic_read(&last_readahead_pages)); if (!hits) - prev_offset = offset; + WRITE_ONCE(prev_offset, offset); atomic_set(&last_readahead_pages, pages); return pages; -- 2.25.1